Improvement in safety-valves



UNITED STATES PATENT OEEICE.

JOHN Y. SMITH, OF ALEXANDRIA, VIRGINIA.

IMPROVEMENT IN SAFETY VALVES.

Specification forming part of Letters Patent No. 47,869, dated May 2li,1865.

To all whom, t may concern.-

Be it known that I, JOHN Y. SMITH, of Alexandria, in the county ofAlexandria and State of Virginia, have invented certainnew and usefulImprovements in Safety-Valves for SteanIGeiierators 5 and I herebydeclare that the following, taken in connection with the accompanyingdrawings, is such full, clear, and

exact description as will enable others skilled in the art to make anduse the same.

On locomotive-boilers and other steamgen erators the safety-valve mostlyused consists of a cap fitting an opening` in the top of the boiler,which cap is' held down by means of a lever weighted or spring-balancedto the proper degree of pressure. The dangers attending the use of thissafety-valve arise, first, from the fact, well known to engineers, thatthe cap becomes fast or, as it were, cemented into its seat as soon asthe vibration attending the operation ofthe en gine ceases; second, fromthe fact that the safety-valve is under the control of engineers, whovery frequently recklessly tamper with the valve so as to prevent itfrom blowing off steam when its pressure exceeds the calculatedresistance of the boiler.

To obviate these evils is the object of my invention, and I haveaccomplished the same by construct-ing a safetyvalve in the followingmanner:

The principle which underlies my invention consists in the employment,in lieu of the cap, of a disk made of sheet metal or composition struckoff or punched out by suitable dies or machinery. i. rIhis disk is of aresistance to pressure upon its surface equal to that which iscalculated to be thelimit of pressure to which the boiler may be withsafety exposed. The disk is inserted in the boiler, so as to beinaccessible to the engineer, by means of a skeleton valve, of which thedisk forms apart, and which, together with the disk, operates likeanordinary safety-valve. When 'the pressure in the boiler exceeds thelimit of safety, then the disk will burst, allowing steam to escapethrough the skeletoirvalvc. v

The valve-case may be provided with a stopcock to shut oft' the steamafter the bursting of the disk; but in order to prevent tampering on thepart of the engineer I propose to com' bine with the disk a pendent rodwhich traverses the way in the cock, preventing it from or outsidethevalvecase, the rod abuttingV against the skeleton-valve or the outsidelever to lift the valve when the temperature increases and exceeds thatcorresponding to the pressure of safety.

In the accompanying drawings, A is the valve-case, which may be screwedin or bolted over the opening of the boiler or steam-dome. It is hereshown provided with a stop-cock, 13, for the purpose before mentioned.The upper end of the valve-case is formed into a conical seat, againstwhich is fitted the valve composed of three parts, viz., first, askeleton valve C, which consists of a valve-ring whose outer and lowerface is made to fit the valve-seat, with downward-projecting wings fw,whereby the valve in its up-and-down play is securely guided, and aninternal annular shoulder, a. Upon this shoulder rests secondly, a metaldisk, D. This is composed of brass, iron, or

other suitable material, such as will break or l tear under a pressureexceeding that of calculated resistance. This metal disk is held inplace by, thirdly, a skeleton cap, E--zZ c., a ring directly oppositethe shoulder a, from which ring spring ribs terminating into the seat Fof the pintle or fulcrum pin ofthe weighted or spring-balanced lever.

The operation of this contrivance, it will be understood, is preciselylike that of any othercombine With the disk the rod It, which,traversing the aperture in the cock, prevents it from being shut off,which would defeat the object of my safety contrivance.

In Figure 2 I have shown the expansion device before referred to. Itconsists of a steel cage having in itscenter a brass rod,`s,

traversing a disk, L, which is properly screwedunder a pressureexceedingthat of safety.

2. The construction of the valve' of three parts, substantially asherein described7 and for the purposes set forth.

8. In combination with a safety-valve constructed and operating asdescribed, the stopcock7 for the purpose set forth.

4. In combination with avvalve and valvecase provided with a stop-cock,as described, v

the pendent rod fast to the disk, substantially as set forth.

In testimony whereof I have signed my name to this specification beforetwo subscribing Witnesses.

` J. Y. SMITH.

Witnesses A. POLLAK, Jos. L. CooMBs.

